Diplexer duplexer and two-channel mobile communications equipment

ABSTRACT

A diplexer employed in mobile communications equipment such mobile phones which can divide signals into two channels with a simple configuration without interfering the other band. In this diplexer, an inductor  105  is connected between a π-type three-stage one polar low-pass filter  115  and a common terminal  113  as a first matching circuit, and a capacitor  106 A is connected between a one polar band-pass filter  116  and a common terminal  113  as a second matching circuit so that interference with the other band can be prevented and the higher harmonics can be sufficiently attenuated with simple configuration.

This Application is a U.S. National Phase Application of PCTInternational Application PCT/JP976/03381.

FIELD OF THE INVENTION

The present invention relates to the field of diplexers, duplexers, andtwo-channel mobile communications equipment employed in mobilecommunications, particularly in mobile phones.

BACKGROUND OF THE INVENTION

Diplexers employed in mobile communications generally have theconfiguration shown in FIGS. 9 to 11. Specifically, a diplexer of theprior art has a circuit shown in FIG. 9 which comprises a low-passfilter and high-pass filter formed in a low-dielectric ceramic materialas shown in FIG. 10.

In FIG. 10, a conductive layer 24 is formed on a low-dielectric layer 16i as a shield electrode, followed by a laminated low-dielectric layer 16h. Inductor electrodes 23 a and 23 b are formed on this low-dielectriclayer 16 h, followed by a laminated low-dielectric layer 16 g. Acapacitor electrode 22 is formed on this low-dielectric layer 16 g,followed by a laminated low-dielectric layer 16 f. A capacitor electrode21 is formed on this low-dielectric layer 16 f, followed by a laminatedlow-dielectric layer 16 e. A conductive layer 20 is formed on thislow-dielectric layer 16 e as a shield electrode, followed by a laminatedlow-dielectric layer 16 d. Capacitor electrodes 19 a and 19 b are formedon this low-dielectric layer 16 d, followed by a laminatedlow-dielectric layer 16 c. An inductor electrode 18 is formed on thislow-dielectric layer 16 c, followed by a laminated low-dielectric layer16 b. An inductor electrode 17 is formed on this low-dielectric layer 16b, followed by a laminated low-dielectric layer 16 a. In thelow-dielectric layer 16 b, a via hole 25 is formed to create anelectrical connection between the inductor electrodes 17 and 18.

Next, FIG. 11 shows a perspective of the diplexer of the prior art. Theconductive layers 20 and 24 are connected with end electrodes 26 b, 26d, 26 f, and 26 g at the side of the dielectric substance to form ashielded electrode by grounding the end electrodes 26 b, 26 d, 26 f, and26 g.

Also, as shown in FIG. 9, a first terminal 907 is formed by connectingan end electrode 26 a and the inductor electrode 17 at the side of thedielectric substance, and a first inductor 902 is also formed byconnecting the inductor electrodes 17 and 18 through the via hole 25.The end electrode 26 a is also connected to the capacitor electrode 19 aat the side of the dielectric substance to form a first capacitor 901between the conductive layer 20. A common terminal 908 is formed byconnecting the inductor electrode 18 and capacitor electrode 21 to anend electrode 26 c at the side of the dielectric substance. The endelectrode 26 c is further connected to the capacitor electrode 19 b atthe side of the dielectric substance to form a second capacitor 903between the conductive layer 20. This is how a low-pass filter 910 isconfigured.

Next, a third capacitor 905 is formed with the capacitor electrode 22facing the capacitor electrode 21 connected to the end electrode 26 c.The end electrode 26 c is also connected to the inductor electrode 23 bat the side of the dielectric substance, and a second inductor 904 isformed by connecting the other end of the inductor electrode 23 b to theend electrode 26 g. In the same way, the capacitor electrode 22 isconnected to the inductor electrode 23 a at the side of the dielectricsubstance, and a third inductor 906 is formed by connecting the otherend to the end electrode 26 f. The capacitor electrode 23 is alsoconnected to the end electrode 26 e at the side of the dielectricsubstance to form a second terminal 909. This is how a high-pass filter911 is configured.

Attenuation of the low-pass filter 910 is increased in the passbandfrequency of the high-pass filter 911, and attenuation of the high-passfilter 911 is increased in the passband frequency of the low-pass filter910 to ensure mutual isolation.

However, since the number of mobile communications users has rapidlyincreased in recent years, the trend is towards enabling the use of asystem employing two different frequency bands in one piece ofcommunications equipment to make it more likely to secure acommunications channel. In this case, a device for dividing two bands isrequired. If the diplexer of the prior art which comprises a low-passfilter and high-pass filter formed in a low-dielectric ceramic materialis used for realizing such a system, due to structural limitations, thehigher harmonics cannot be removed. In addition, the size will be largerdue to design restrictions.

SUMMARY OF THE INVENTION

The present invention offers a small device for dividing two bands andalso removing the higher harmonics.

The present invention has a configuration comprising a formedlow-dielectric layer and high-dielectric layer. A low-pass filter and aninductor as a matching circuit for the low-pass filter are formed in thelow-dielectric layer, and a band-pass filter and a capacitor as amatching circuit for the band-pass filter are formed in thehigh-dielectric layer.

This configuration allows the present invention to be embodied in asmall device which can divide signals input to a common terminal intotwo bands and remove the higher harmonics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit showing the configuration of a diplexer in a firstexemplary embodiment of the present invention.

FIG. 2 shows a configuration of a diplexer in accordance with a secondexemplary embodiment of the present invention.

FIG. 3 is a perspective of the diplexer in accordance with the secondexemplary embodiment of the present invention.

FIG. 4 is a circuit diagram of the diplexer in accordance with thesecond exemplary embodiment of the present invention.

FIG. 5 shows another configuration of the diplexer in accordance withthe second exemplary embodiment of the present invention.

FIG. 6 is a circuit diagram showing another configuration of a resonatorelectrode in the diplexer in accordance with the second exemplaryembodiment of the present invention.

FIG. 7 is a circuit diagram of a duplexer in accordance with a thirdexemplary embodiment of the present invention.

FIG. 8 is a circuit diagram of a duplexer in accordance with a fourthexemplary embodiment of the present invention.

FIG. 9 is a circuit diagram of a diplexer in accordance with the priorart.

FIG. 10 shows a configuration of the diplexer in accordance with theprior art.

FIG. 11 is a perspective of the diplexer in accordance with the priorart.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Exemplary Embodiment

FIG. 1 shows a circuit diagram of a diplexer in a first exemplaryembodiment of the present invention. In FIG. 1, one end of a firstcapacitor 101, one end of a first inductor 102, and one end of a secondcapacitor 103 are connected to a first terminal 112, and the other endof the first capacitor 101 is grounded. The other end of the firstinductor 102 and the other end of the second capacitor 103 are connectedto one end of a third capacitor 104 and one end of a second inductor105. The other end of the third capacitor 104 is grounded. The other endof the second inductor 105 is connected to one end of a fourth capacitor106A in series, and it is also connected to a common terminal 113. Theother end of a fourth capacitor 106B is connected to a first quarterwavelength resonator 107, one end of a fifth capacitor 108, and one endof a third inductor 109. The other end of the fifth capacitor 108 isconnected to a second quarter wavelength resonator 110 and one end of asixth capacitor 111. The other end of the third inductor 109 isconnected to the other end of the sixth capacitor 111 to connect to asecond terminal 114.

To simplify the description, the fourth capacitors 106A and 106Bconnected in series are represented by one capacitor, which is a fourthcapacitor 106 in the following explanation.

The operation of the diplexer as configured above is now explained.

The first capacitor 101, first inductor 102, second capacitor 103, andthird capacitor 104 form a π-type three-stage one polar low-pass filter115. The first band is set to a passband, and an attenuation pole isformed in the second band. The fourth capacitor 106, first quarterwavelength resonator 107, fifth capacitor 108, third inductor 109,second quarter wavelength resonator 110, and sixth capacitor 111 formtwo-stage one polar band-pass filter 116. The second band is set to apassband and an attenuation pole is formed in the first band.

In a circuit from the common terminal 113 to the second terminal 114,impedance of the fourth capacitor 106 connected in series can be definedas 1/(ωC), where C is the capacity. Since the first quarter wavelengthresonator 107 can be equivalently replaced with a parallel resonancecircuit of a capacitor and inductor with one end grounded, thenimpedance of the capacitor and inductor can be defined respectively asωC and 1/(ωL) (L is inductance of the inductor). This makes impedance ofthe fourth capacitor 106 higher and impedance of the first quarterwavelength resonator 107 lower as the frequency lowers.

Accordingly, in the first band, the band-pass filter 116 showscapacitive characteristics, and functions as a capacitor connectedbetween the common terminal 113 and ground. With the second inductor 105connected as the first matching circuit, an area between the firstterminal 112 and common terminal 113 becomes equivalent to a π-typefive-stage low-pass filter.

This allows to sufficiently attenuate signals in the first band input tothe common terminal 113 at the second terminal 114 side, and the most ofsuch signals are output to the first terminal 112 side. In addition, thehigher harmonics is sufficiently attenuated by the low-pass filter 115.On the contrary, signals in the first band input to the first terminal112 do not pass through to the second terminal 114 side, and are outputto the common terminal 113.

Next, the operation between the common terminal 113 and second terminal114 is explained. In a circuit between the common terminal 113 and firstterminal 112, impedance of the second inductor 105 connected in seriescan be defined as ωL where L is inductance. Impedance of the thirdcapacitor 104 connected before the ground can be defined as 1/(ωC) (C iscapacitance of the capacitor). Thus, impedance of the second inductor105 becomes higher and impedance of the third capacitor 104 becomeslower as the frequency increases. Accordingly, the low-pass filter 115shows inductivity in the second band, and functions as an inductorconnected between the common terminal 113 and ground.

Here, suppose that a capacitor is connected in series between the commonterminal 113 and pass-band filter 116, and an inductor is connectedbetween the other end of the capacitor, contact point of the band-passfilter 116, and ground. This inductor then is equivalent to a negativecapacitor connected between the ground, and it can also be replaced withthe first quarter wavelength resonator 107 by making the resonatorlength shorter. Furthermore, since input/output connection of theband-pass filter 116 is capacitive coupling, the capacitor can be formedwith a single element as composite capacitance.

As a result, the circuit shown in FIG. 1 can be configured to include aninductor connected between the capacitor, which is connected in seriesbetween the common terminal 113 and band-pass filter 116, and the groundby adjusting the fourth capacitor 106 and the resonator length of thefirst quarter wavelength resonator 107.

Therefore, in the second band, between the common terminal 113 and thesecond terminal 114, the inductor connected to the ground, capacitorconnected in series, and inductor connected to the ground are configuredequivalently. This circuit functions as a matching circuit in the bandlower than the passband, which is commonly known as a phase shifter ofthe π-type high-pass filter.

This allows sufficient signal attenuation in the second band input tothe common terminal 113 at the first terminal 112 side, and most of suchsignals are output to the second terminal 114 side. The higher harmonicsare also sufficiently attenuated by the pass-band filter 116. On thecontrary, signals in the second band input to the second terminal 114 donot pass through to the first terminal 112 side, and are output to thecommon terminal 113.

With the above configuration, the present invention functions as adiplexer which divides input signals into two bands.

There are other circuit configurations for configuring the one polarband-pass filter. The details of the diplexer of the present inventionare not affected by the circuit configuration of the band-pass filter.

In mobile telephone terminals employing two frequency bands, thediplexer of the present invention offers a simple high frequency wavedividing circuit for terminals, allowing terminals to be made smallerand lighter.

Second Exemplary Embodiment

FIG. 2 shows the configuration of a diplexer in a second exemplaryembodiment of the present invention. FIG. 3 is a perspective diagram ofthe same diplexer. In FIG. 2, a conductive layer 13 is formed as ashield electrode on a low-dielectric layer 3 mainly composed ofSiO₂—Al₂O₃—MO (M consists of at least one of Ba, Ca, and Sr)−La₂O₃—B₂O₃glass, and then a high-dielectric layer 2 c, composed of Bi₂O₃—CaO—Nb₂O₅dielectric ceramic material, Bi₂O₃—CaO—ZnO—CuO—Nb₂O₅ dielectric ceramicmaterial, or BaO—Nd₂O₅—TiO₂ dielectric ceramic material is laminated onthe low-dielectric layer 3. Resonator electrodes 12 a and 12 b areformed on this high-dielectric layer 2 c, and then a high-dielectriclayer 2 b composed of Bi₂O₃—CaO—Nb₂O₅ dielectric ceramic material,Bi₂O₃—CaO—ZnO—CuO—Nb₂O₅ dielectric ceramic material, or BaO—Nd₂O₅—TiO₂dielectric ceramic material is laminated on the high-dielectric layer 2c. A capacitor electrode 11 is disposed on this high-dielectric layer 2b for forming a second matching circuit with the capacitor electrode 9for input/output coupling and load capacitor electrodes 10 a and 10 b. Ahigh-dielectric layer 2 a composed of the same Bi₂O₃—CaO—Nb₂O₅dielectric ceramic material, Bi₂O₃—CaO—ZnO—CuO—Nb₂O₅ dielectric ceramicmaterial, or BaO—Nd₂O₅—TiO₂ dielectric ceramic material is laminated onthe high-dielectric layer 2 b. On top of this high-dielectric layer 2 a,a conductive layer 8 is formed as a shield electrode.

Next, on the high-dielectric layer 2 a where the conductive layer 8 isprovided, a low-dielectric layer 1 d mainly composed ofSiO₂—Al₂O₃—MO—La₂O₃—B₂O₃ glass is provided. On top of thislow-dielectric layer 1 d, capacitor electrodes 7 a and 7 b are formed,and then a low-dielectric layer 1 c mainly composed ofSiO₂—Al₂O₃—MO—La₂O₃—B₂O₃ glass is provided. On top of thislow-dielectric layer 1 c, a capacitor electrode 6 is formed, and then alow-dielectric layer 1 b mainly composed of SiO₂—Al₂O₃—MO—La₂O₃—B₂O₃glass is provided. On top of this low-dielectric layer 1 b, inductorelectrodes 4 and 5 for forming a first matching circuit are disposed. Ontop of the low-dielectric layer 1 b, a low-dielectric layer 1 a mainlycomposed of the same SiO₂—Al₂O₃—MO—La₂O₃—B₂O₃ glass is provided.

The diplexer as configured above is made by sintering after printing andlaminating using a ceramic green sheet.

Next, materials of the low-dielectric layers 1 a to 1 d and 3, andhigh-dielectric layers 2 a to 2 c which are the characteristic of thepresent invention are explained.

Green sheets of the low-dielectric layers 1 a to 1 d and 3, andhigh-dielectric layers 2 a to 2 c are manufactured respectively asfollows. Glass used for the low-dielectric layers 1 a to 1 d and 3 ismade by melting raw materials such as SiO₂, H₃BO₃, Al(OH)₃, CaCO₃,BaCO₃, SrCO₃, and La₂O₃ in platinum or platinum-rhodium crucible andgrinding into glass powder after cooling. Then, 500 g glass powder madein the above way is added to a solution comprising 200 g methyl ethylketone, 25 g dibutyl phthalate, and 50 g polyvinyl butyral resin, andmixed and ground for 24 hours in a ball mill to make a slurry. A 50 μmthick green sheet of low-dielectric layer is made from the slurry usingthe known doctor blade method.

A Bi₂O₃—CaO—Nb₂O₅ (hereafter referred to as BCN) high-dielectric layeris made by adding 500 g BCN dielectric powder with a dielectric constantof 58, as disclosed in Japanese Laid-open Patent No. H5-225826, to asolution comprising 200 g methyl ethyl ketone, 10 g dibutyl phthalate,and 25 g polyvinyl butyral resin, and mixing for 24 hours in a ball millto make a slurry. A 50 μm thick green sheet of BCN high-dielectric layeris made from the slurry using the doctor blade method.

A Bi₂O₃—CaO—ZnO—CuO—Nb₂O₅ (hereafter referred to as BCZCN)high-dielectric layer is made by adding 500 g BCZCN dielectric powderwith a dielectric constant of 100 to a solution comprising 200 g methylethyl ketone, 10 g dibutyl phthalate, and 25 g polyvinyl butyral resin,and mixing in a ball mill for 24 hours to make a slurry. A 50 μm thickgreen sheet of BCZCN high-dielectric layer is made from the slurry usingthe doctor blade method.

In the same way, a BaO—Nd₂O₅—TiO₂—Bi₂O₃ high-dielectric layer is made byadding 20 weight % of SiO₂—Al₂O₃—MO (consisting of at least one of Ba,Ca, and Sr)−La₂O₃—B₂O₃ glass powder to 100 weight % ofBaO—Nd₂O₅—TiO₂—Bi₂O₃ high-dielectric powder with a dielectric constantof 60, as disclosed in Japanese Laid-open Patent No. H9-108788, to make500 g powder mixture. This powder (hereafter referred to as BNTG) isadded to a solution comprising 200 g methyl ethyl ketone, 10 g dibutylphthalate, and 25 g polyvinyl butyral resin, and mixed in a ball millfor 24 hours to make a slurry. A 50 μm thick green sheet of a BNTGhigh-dielectric layer is made from the slurry using the doctor blade.

The composition of BaO—Nd₂O₅—TiO₂—Bi₂O₃ dielectric material is explainedin details in a fifth exemplary embodiment.

The high-dielectric layer sheets made in accordance with the abovemethods are laminated, and pressed by thermo-compression at 60° C. Inthis process between the 600 μm thick high-dielectric layers 2 a and the50 μm thick high-dielectric layer 2 b, input/output coupling capacitor9, load capacitor electrodes 10 a and 10 b, and capacitor electrode 11for the second matching circuit is formed, and between the 50 μm thickhigh-dielectric layer 2 b and the 600 μm thick high-dielectric layers 2c, the resonator electrode 12 a and 12 b is formed. In the same way, thelow-dielectric layer sheets are laminated and pressed by thermalcompression at 60° C. to make the low-dielectric layers 1 a to 1 d and3. Via holes 14 a and 14 b are made in the low-dielectric layer 1 b tocreate conductivity between the conductive layers, and silver paste isfilled into the via holes 14 a and 14 b. On green sheets of thelow-dielectric layers 1 b to 1 d, and 3, silver paste is printed in aspecified conductive pattern respectively using the screen printingmethod to respectively form the inductor electrode 4, inductor electrode5 for matching circuit, capacitor electrode 6, capacitor electrodes 7 aand 7 b, conductive layer 8, and conductive layer 13. Then, green sheetsof the low-dielectric layers 1 a to 1 d pressed by thermo-compression,high-dielectric layer 2 a to 2 c pressed by thermo-compression, and thelow-dielectric layer 3 are positioned in order and laminated, pressed bythermal compression at 80° C., de-bindered at 400 to 450° C., andsintered at 900 to 950° C.

Next, silver paste is printed and sintered using the screen printingmethod to form the end electrodes 15 a to 15 e shown in FIG. 3 at theside of the sintered substance for connecting the sintered substancewith a printed circuit board. Nickel and solder plated layers are thenformed using barrel plating.

The operation of the diplexer as configured above is now explained.

The diplexer as configured above is equivalent to a circuit shown inFIG. 4. In general, it is the same as the diplexer explained in thefirst exemplary embodiment. Detailed explanation is therefore omittedhere by allocating the same numerals to the same parts.

The conductive layer 8 and conductive layer 13 are connected to the endelectrodes 15 a and 15 d at the side of the dielectric substance, and ashield electrode is formed by grounding the end electrodes 15 a and 15d.

At the side of the dielectric substance, the end electrode 15 b andinductor electrode 4 are connected to form the first inductor 102 withthe first terminal 112, and the end electrode 15 b is also connected tothe capacitor electrode 7 a. The capacitor electrode 7 a forms the firstcapacitor 101 with the conductive layer 8, and also forms the secondcapacitor 103 by disposing the capacitor electrode 6 to face a part ofthe inductor electrode 4. The inductor electrode 4 and capacitorelectrode 6 are connected through the via hole 14 b. In addition, theinductor electrode 5 for matching circuit, capacitor electrode 6, andcapacitor electrode 7 b are connected through the via hole 14 a to formthe second inductor 105. The capacitor electrode 7 b forms the thirdcapacitor 104 between the conductive layer 8.

A low-pass filter 415 is configured as above, and the common terminal113 is formed by connecting the inductor electrode 5 for matchingcircuit and end electrode 15 e at the side of the dielectric substance.

Next, the end electrode 15 e is connected to the capacitor electrode 11for the matching circuit. The end electrode 15 e forms the commonterminal 113, and the capacitor electrode 11 for the matching circuitforms the fourth capacitor 106 by disposing it to face a part of theresonator electrode 12 b. The end electrode 15 c is connected to theinput/output coupling capacitor electrode 9 to form the second terminal114. The input/output coupling capacitor electrode 9 forms the sixthcapacitor 111 by disposing it to face a part of the resonator electrode12 a. One end of the resonator electrode 12 b is connected to thegrounded end electrode 15 a to form a first quarter wavelength resonator417. In the same way, one end of the resonator electrode 12 a isconnected to the grounded end electrode 15 a to form a second quarterwavelength resonator 418. The load capacitor electrode 10 b is disposedto face a part of the resonator electrode 12 b, and one end of the loadcapacitor electrode 10 b is connected to the grounded end electrode 15 cto form a first load capacitor 419. The load capacitor electrode 10 a isdisposed to face a part of the resonator electrode 12 a, and one end ofthe load capacitor electrode 10 a is connected to the grounded endelectrode 15 c to form a second load capacitor 420. Accordingly, aband-pass filter 416 is configured.

The band-pass filter 416 made in the high-dielectric layers 2 a to 2 cforms an attenuation pole by electromagnetic connection between thefirst quarter wavelength resonator 417 and second quarter wavelengthresonator 418. It is set to form a passband in the second band and theattenuation pole in the first band. In the second band, the low-passfilter 415, as in the first exemplary embodiment, functions as aninductor connected between the common terminal 113 and ground. Here, aphase shifter of π-type high-pass filter type is configured by adjustingthe resonator length of the first quarter wavelength resonator 417 andcapacitance of the first load capacitor 419. By employing theconfiguration to laminate two types of dielectric layers into one piece,the diplexer can be made smaller and shorter.

With the above configuration, the second exemplary embodiment operatesas a diplexer which divides input signals to two bands.

In this exemplary embodiment, a shield electrode is disposed between thelow-dielectric layer and high-dielectric layer. As shown in FIG. 5, itis also possible to form conductive layers 16 a, 16 b, 17 a and 17 brespectively as shield electrodes inside the low-dielectric layer andhigh-dielectric layer. This will further suppress dispersion in thecharacteristics of the band-pass filters and reduce manufacturing costsbecause diffusion of high-dielectric ceramic material to low-dielectricceramic material during sintering can be reduced, which furtherfacilitates sintering of the dielectric substance.

In this exemplary embodiment, capacitive coupling is employed asinput/output coupling for the band-pass filter. As shown in FIG. 6, atapping electrode 621 can also be employed for connection. This has theadvantage of easier impedance matching of the band-pass filter with abroader band and lower insertion loss.

Furthermore, in mobile telephone terminals for two channels, thediplexer of the present invention offers a simpler high frequency wavedividing circuit for terminals, allowing terminals to be made smallerand lighter.

Third Exemplary Embodiment

FIG. 7 shows a configuration of a duplexer in a third exemplaryembodiment of the present invention. In FIG. 7, a common terminal of afirst diplexer 702 is connected to one output terminal of a single polardouble transmission switch (hereafter referred to as SPDT switch 701,and a common terminal of a second diplexer 703 is connected to the otheroutput terminal of the SPDT switch 701. In this way, the duplexer isconfigured with an input terminal of the SPDT switch 701 as an antennaterminal 704, a first terminal of the first diplexer 702 as a firsttransmission terminal 708, a second terminal of the first diplexer 702as a second transmission terminal 709, a first terminal of a seconddiplexer 703 as a first receiving terminal 711, and a second terminal ofthe second diplexer 703 as a second receiving terminal 712.

The operation of the duplexer as configured above is now explained.

The diplexer employed in this exemplary embodiment is the same as thatexplained in the first and second exemplary embodiments. Detailedexplanation of its operation is thus omitted.

In mobile telephone terminals adopting the TDMA system, transmission andreceiving does not take place simultaneously. Therefore, the SPDT switch701 which switches the channel timewise can be employed.

The first diplexer 702 prevents transmission signals in the first bandinput to the first transmission terminal 708 from flowing to the secondtransmission terminal 709, and outputs them to the common terminal 707of the first diplexer. These transmission signals in the first band thenflow to the first output terminal 705 of the SPDT switch 701. The SPDTswitch 701 prevents signals in the first band from flowing to the secondoutput terminal 706, and outputs them from the antenna terminal 704. Inthe same way, the first diplexer 702 prevents transmission signals inthe second band input to the second transmission terminal 709 fromflowing to the first transmission terminal 708, and outputs them to thecommon terminal 707 of the first diplexer 702. These transmissionsignals in the second band then flow to the first output terminal 705 ofthe SPDT switch 701. The SPDT switch 701 prevents signals in the secondband from flowing to the second output terminal 706, and outputs themfrom the antenna terminal 704.

Next, the SPDT switch 701 prevents receiving signals in the first bandinput to the antenna terminal 704 from flowing to the first outputterminal 705 and outputs them to the second output terminal 706. Thesereceiving signals in the first band then flow to the common terminal 710of the second diplexer 703. The second diplexer 703 prevents thesesignals in the first band from flowing to the second receiving terminal712, and outputs them to the first receiving terminal 711. In the sameway, the SPDT switch 701 prevents receiving signals in the second bandinput to the antenna terminal 704 from flowing to the first outputterminal 705, and outputs them to the second output terminal 706. Thesereceiving signals in the second band then flow to the common terminal710 of the second diplexer 703. The second diplexer 703 prevents thesesignals in the second band from flowing to the first receiving terminal711, and outputs them to the second receiving terminal 712.

With the above configuration, the third exemplary embodiment functionsas a duplexer corresponding to the TDMA system for using the twofrequency bands.

The present invention thus can be employed as a duplexer for twosystems, for example, Personal Digital Cellular (PDC) and Personal HandyPhone System (PHS) by using PDC in the first band and PHS in the secondband.

The present invention can also be employed as a duplexer for twosystems, for example, the European standard Group Special Mobile (GSM),and the European Personal Communications Network (PCN), by using GSM inthe first band and PCN in the second band.

There is a wide variety of types of SPDT switches, but the duplexer usedin the present invention is not affected by the type of SPDT switch. Formobile telephone terminals employing two frequency bands, the use of theduplexer of the present invention enables the common circuit of theterminals to be simply configured, allowing the terminal to be madesmaller and lighter.

Fourth Exemplary Embodiment

FIG. 8 shows the configuration of a duplexer in a fourth exemplaryembodiment of the present invention. In FIG. 8, an antenna terminal 807of a first duplexer 802 is connected to a first terminal 805 of adiplexer 801, and an antenna terminal 810 of a second duplexer 803 isconnected to a second terminal 806. In this way, a duplexer isconfigured with a common terminal of the diplexer 801 as an antennaterminal 804, a transmission terminal of the first duplexer 802 as afirst transmission terminal 808, a receiving terminal of the firstduplexer 802 as a first receiving terminal 809, a transmission terminalof the second duplexer 803 as a second transmission terminal 811, and areceiving terminal of the second duplexer 803 as a second receivingterminal 812.

The operation of the duplexer as configured above is now explained.

The diplexer employed in this exemplary embodiment is the same as thatexplained in the first and second exemplary embodiments. Detailedexplanation of its operation is thus omitted.

Transmission and receiving are executed at the same time in mobiletelephone terminals adopting systems other than the TDMA system.Therefore, the SPDT switch, which switches the channels timewise, cannotbe employed. Accordingly, signals in the first band and second band arefirst divided by the diplexer, and then separated to transmission andreceiving signals in each band.

The first duplexer 802 prevents transmission signals in the first bandinput to the first transmission terminal 808 from flowing to the firstreceiving terminal 809. Instead, they are output to the antenna terminal807 of the first duplexer, and then to the first terminal 805 of thediplexer 801. The diplexer 801 prevents these signals in the first bandfrom flowing to the second terminal 806, and outputs them from theantenna terminal 804. The diplexer 801 prevents receiving signals in thefirst band input to the antenna terminal 804 from flowing to the secondterminal 806. Instead, they are output to the first terminal 805, andthen to the antenna terminal 807 of the first duplexer 802. The firstduplexer 802 prevents signals in the first band from flowing to thefirst transmission terminal 808, and outputs to the first receivingterminal 809.

Then, transmission signals in the second band input to the secondtransmission terminal 811 are prevented from flowing to the secondreceiving terminal 812 by the second duplexer 803. Instead, they areoutput to the antenna terminal 810 of the second duplexer, and then tothe second terminal 806 of the diplexer 801. The diplexer 801 preventsthese signals from flowing to the first terminal 805, and outputs themfrom the antenna terminal 804. The diplexer 801 prevents receivingsignals in the second band input to the antenna terminal 804 fromflowing to the first terminal 805. Instead, they are output to thesecond terminal 806 and then to the antenna terminal 810 of the secondduplexer 803. The second duplexer 803 prevents these signals fromflowing to the second transmission terminal 811, and outputs to thereceiving terminal 812.

With the above configuration, this exemplary embodiment functions as aduplexer for systems other than the TDMA system for using the twofrequency bands.

The duplexer of the present invention thus can be employed for twosystems, for example, Advanced Mobile Phone Service (AMPS), which is ananalog mobile phone in the US, and Personal Communications Systems(PCS), which is a personal mobile communications system in the US, byusing AMPS in the first band and PCS in the second band.

Furthermore, for mobile telephone terminals employing two frequencybands, the use of the duplexer of the present invention enables thecommon circuit of the terminals to be simply configured, allowing theterminal to be made smaller and lighter.

Fifth Exemplary Embodiment

The composition of BaO—Nd₂O₅—TiO₂—Bi₂O₃ dielectric material used in ahigh-dielectric layer of the aforementioned diplexer of the presentinvention is explained next. This material is made by mixing the firstpowder component and second powder component at a specified ratio. Thefollowing explanation uses these expressions.

First, the composition of the first powder component is explained. Assource materials, chemically high purity (99 weight % or above) ofBaCO₃, Nd₂O₃, TiO₂, and Bi₂O₃ are used. After adjusting the purity ofthe source substance, each source substance is weighed to achieve aspecified values of x, y, z, and w when defined asxBaO—yNd₂O₃—zTiO₂—wBi₂O₃ (x+y+z+w=1). These powders are mixed in a ballmill with zirconia stones and pure water for 17 hours to make a slurry.After mixing, the slurry is dried and kept in an alumina crucible forprovisional sintering for 2 hours at 1000 to 1300° C. Provisionallysintered slurry is crushed and ground in the ball mill for 17 hours, anddried to complete the first powder component.

The composition of the second powder component is explained next. Sourcematerials are chemically high purity (99 weight % or above) substancessuch as SiO₂, H₃BO₃, Al₂(OH)₃, CaCO₃, BaCO₃, SrCO₃, and La₂O₃. Aftercorrecting purity of the source substances, they are weighed inaccordance with the composition shown in Table 1. Powder of thesesubstances are mixed and kept in a platinum or platinum-rhodium crucibleto melt at 1400 to 1500° C. and cooled rapidly. After crushing, the samemethod as mixing is used for grinding, and dried to make the secondpowder component. The composition and characteristics of the mixedsecond component are shown in Table 1.

TABLE 1 Specimen Composition of the second component (weight %) No. SiO₂La₂O₃ BaO CaO SrO B₂O₃ Al₂O₃ ZrO₂ LiO₂ K₂O A 45 10 20 15 5 5 B 40 15 2510 5 5 C 45 10 20 15 5 5 D 45 10 25 5 5 5 5 E 45 10 20 15  5 5

The first and second powder components are weighed in the ratio shown inTable 2, wet blended in the ball mill, and then dried. Average particlediameter of this mixed powder is measured using the laser diffractionmeasuring method. After adding 8 weight % of a 5 weight % polyvinylalcohol solution as a binder and mixing them, mixed powder is granulatedusing a 32-mesh sifter, and pressed with a disc of 13 mm diameter andabout 5 mm thickness under 100 Mpa. Pressed powder is heated at 60020 C.for 3 hours to bum out the binder, kept in a magnesia porcelaincontainer, covered with a lid, and sintered at temperatures rangingbetween 800 and 1100° C. for 2 hours. The dielectric characteristics ofthe sintered body sintered at the temperature which makes the maximumdensity were measured using microwaves. Resonance frequency and Q valuewere calculated in accordance with the dielectric resonance method.Relative dielectric constant (∈r) is calculated from the dimensions andresonance frequency of the sintered substance. Resonance frequency wasbetween 2 and 7 GHz.

Resonance frequency at −25° C., 20° C., and 85° C. was then measured tocalculate its temperature coefficient (τf) using the method of leastsquare. The deflective strength of the sintered substance was alsomeasured using the method in accordance with JIS R1601. Results areshown in Table 2. The Qf product in Table 2 is the Q value multiplied bythe frequency f at which Q value is measured. The frequency f is between2 and 7 GHz depending on the size and shape of the specimen. The Qfproduct is thus calculated to obtain a value independent of the size orshape of the specimen. This is the method generally used in theindustry.

As shown in Table 2, Specimens Nos. 2 to 15, which have a porcelaincomposition applicable to this exemplary embodiment were sintered atbetween 925° C. and 105° C., showing excellent microwave dielectriccharacteristics: Relative dielectric constant (∈r) between 41 and 88, Qfproduct between 1200 and 3300 GHz, and temperature coefficient (τf) ofresonance frequency between 15 and 45 ppm/° C. The deflective strengthof these porcelains were all above 180 Mpa, which is larger than thedeflective strength of a conventional Bi₂O₃—CaO—Nb₂O₅ material with 140Mpa.

The composition of the second component glass showed good dielectriccharacteristics in the range of compositions between Specimen No. 5 and8. This demonstrates that any glass containing SiO₂, MO (M contains atleast one of Ba, Ca, and Sr), and La₂O₃ can be used as the secondcomponent.

TABLE 2 Composition of Mixing ratio the first component of the secondSpecimen (mol %) component Ts Characteristics No. x y z w Type Wt %(C.°) εr Qf τf σs  1# 15 15 67 3 A  1 nst  2 15 15 67 3 A  3 1050  883300 +10  240  3 15 15 67 3 A  5 1025  82 3300 +3 210  4 15 15 67 3 A 10975 72 3000 +1 200  5 15 15 67 3 B 10 975 69 1800 +8 210  6 15 15 67 3 C10 1000  71 3100 −5 200  7 15 15 67 3 D 10 975 71 2200 −2 190  8 15 1567 3 B 10 1000  70 2800 +4 200  9 15 15 67 3 A 20 950 60 2800 −4 200 1018 18 61 3 A 20 975 51 1300 +10  190 11 11 11 75 3 A 20 950 64 2400 +45 210 12 11 18 68 3 A 20 950 55 2200 −8 210 13 18 11 68 3 A 20 950 62 1600+1 190 14 14 14 67 3 A 20 925 57 2400 −10  180 15 15 15 67 3 A 50 925 411200 −15  180  16# 15 15 67 3 A 60 900 36  750 −25  nmd  17# 15.5 15.569 0 A 10 1025 74 2900 +78  nmd  18# 14.5 14.5 63.5 7.5 A 10 mel — — —nmd  19# 8 22 67 3 A 10 1000 38 3200 −5 nmd  20# 22 8 67 3 A 10 1000 531800 +155  nmd  21# 26 26 45 3 A 10 1025 72 1600 +252  nmd  22# 8 8 81 3A 10 1000 51 2500 +272  nmd x, y, z, w: xBaO—yNd₂O₃—zTiO₂—wBi₂O₃ Ts:Sintered temperature, εr: Relative dielectric constant, Qf: Qf Product,τf: Temperature coefficient, σs: Deflective strength nst: Not sintered,mel: Melted, nmd: Not measured Specimen Nos. marked with # are out ofthe scope of the present invention. Average particle diameter beforesintering the mixed powder is 0.9 μm.

In Specimen No. 1, when the mixing ratio of the second component than 3weight %, it did not sinter at 1100° C. or below, thus not satisfyingthe purpose of the present invention. In Specimen No. 16, when themixing ratio of the second component exceeds 50 weight %, dielectricconstant fell to 40 or below and the Qf product became a small 1000 GHz,which was also not suitable for the present invention.

When x, y, z, and w in xBaO—yNd₂O₃—zTiO₂—wBi₂O₃ (x+y+z+w =1) of thefirst component was out of the range of the present invention, which arespecimens Nos. 17 to 22, relative dielectric constant became smallerthan 40, and temperature coefficient of resonance frequency changed to alarge positive value exceeding +50 ppm/° C., which are not suitable forthe present invention because they do not sinter as porcelain.

Sixth Exemplary Embodiment

Another exemplary embodiments of the second component are explainednext. Characteristics were evaluated using the same method as in thefifth exemplary embodiment. Compositions shown in Table 3 were used forthe second component. Results are shown in Table 4.

As shown in Table 4, specimens Nos. 23 to 28, which are dielectricporcelains within the scope of this exemplary embodiment, were sinteredat a temperature between 925° C. and 975° C. It was confirmed that thesespecimens show good microwave dielectric characteristics, with arelative dielectric constant between 57 and 70, Qf product between 1900and 3200 GHz, and temperature coefficient of resonance frequency between−10 and +3 ppm/° C.; and deflective strength of 180 MPa or above.

TABLE 3 Specimen Composition of the second component (Weight %) No. SiO₂La₂O₃ BaO CaO SrO B₂O₃ Al₂O₃ F  47 15  5 18 10 2 3 G  42 10 20 10 5 13 H  45 10 22 10 8 5 I* 35 10 25 20 5 5 J* 55 10 15 10 5 5 K* 45 10 20 520  L* 45 10 20  5 15  5 M* 45 20 25 5 5 N* 45  2 23 15 10  5

TABLE 4 Composition of Mixing ratio the first component of the secondSpecimen (mol %) component Ts Characteristics No. X y z w Type Wt %(C.°) εr Qf τf σs 23  15 15 67 3 F 10 950 70 2400 −8 190 24  15 15 67 3F 20 925 59 2200 −3 180 25  15 15 67 3 G 10 975 70 3200 −3 220 26  15 1567 3 G 20 975 60 3100 +3 200 27  15 15 67 3 H 10 975 68 2200 −10  20028  15 15 67 3 H 20 950 57 1900 −8 200 29* 15 15 67 3 I 20 950 63  800−3 nmd 30* 15 15 67 3 J 20 1050  58 2500 +5 nmd 31* 15 15 67 3 K 201075  56 2200 +3 nmd 32* 15 15 67 3 L 20 975 61 1500 −3 nmd 33* 15 15 673 M 20 925 55  800 −18  nmd 34* 15 15 67 3 N 20 1050  62 2600 +1 nmd x,y, z, w: xBaO—yNd₂O₃—zTiO₂—wBi₂O₃ Ts: Sintered temperature, εr: Relativedielectric constant, Qf: Qf Product, τf: Temperature coefficient, σs:Deflective strength nst: Not sintered, mel: Melted, nmd: Not measuredAverage particle diameter before sintering the mixed powder is 0.9 μm.

Specimen No. 29, using the second component type I with 40 weight % orless SiO₂, and Specimen No. 33, using the second component type M with15 weight % or above La₂O₃, are not suitable because the Qf product fellbelow 1000 GHz. Specimen No. 30, using the second component type J with50 weight % or more SiO₂, Specimen No. 31, using the second componenttype K with 15 weight % or more Al₂O₃, and Specimen No. 34, using thesecond component type N with 5 weight % or less L₂O₃ demonstrated a highsintering temperature above 1050° C., which is not suitable. SpecimenNo. 32, using the second component L with 10 weight % or more B₂O₃ didnot show any problem with sintering temperature and electricalcharacteristics, but it is unsuitable because it showed extremedifficulty in making a green sheet. When a slurry was made by mixing anappropriate amount of binder, plasticizer, and solvent, and then a greensheet was made using methods such as the doctor blade method, gellationof the slurry occurred.

Seventh Exemplary Embodiment

Next, the effect was examined of further adding copper oxide. Chemicallyhigh purity (99 weight % or above) CuO powder was weighed and mixed withboth first and second components, and specimens were prepared and theircharacteristics were measured in accordance with the same method as thefifth exemplary embodiment. The composition A in Table 1 was employedfor the second component. Results are shown in Table 5.

TABLE 5 Composition of Mixing ratio the first component of the secondCuO Specimen (mol %) component weight Ts Characteristics No. x y z wType Wt % % (C.°) εr Qf f σs  4 15 15 67 3 A 10 0 975 72 3000 +1 200 3515 15 67 3 A 10 0.5 925 71 2900 +3 200 36 15 15 67 3 A 10 1.5 925 692400 −3 200 37 15 15 67 3 A 10 5 900 67 1300 −4 180   38+ 15 15 67 3 A10 7.5 900 67 700 −7 180 x, y, z, w: xBaO—yNd₂O₃—zTiO₂—wBi₂O₃ Ts:Sintered temperature, εr: Relative dielectric constant, Qf: Qf Product,τf: Temperature coefficient, σs: Deflective strength Average particlediameter before sintering the mixed powder is 0.9 μm. It is difficult tomake a green sheet with Specimen No. 32.

It is difficult to make a green sheet with Specimen No. 32.

As shown in FIG. 5, dielectric porcelain with copper oxide showed 50° C.to 75° C. lower sintering temperature compared to dielectric porcelainwithout adding copper oxide. There was no change in electricalcharacteristics. Accordingly, with addition of copper oxide, sinteringtemperature can be always kept below 950° C., so a multi-layer resonancedevice can be made with an internal conductor made of silver, which hashigh conductivity and a melting point of 961° C. In case of Specimen No.38, however, if the amount of CuO added exceeds 5 weight %, which is outof the scope of the present invention, the Qf product fell to 1000 GHzor below, making it not suitable.

Eighth Exemplary Embodiment

Next, the effect was examined of an average particle diameter of mixedpowder. The average particle diameter of mixed powder is adjustable bychanging the mixing duration and diameter of zirconia stone. Results areshown in Table 6.

TABLE 6 Composition of Mixing ratio the first component of the secondSpecimen (mol %) component CuO Particle Ts Characteristics No. x y z wType Wt % (wt %) diameter (C.°) εr Qf τf σs  4 15 15 67 3 A 10 0 0.9 97572 3000 +1 200 39 15 15 67 3 A 10 0 0.75 925 72 2700 +4 220 40 15 15 673 A 10 0 0.6 925 72 2900 +3 230 36 15 15 67 3 A 10 1.5 0.9 925 69 2400−3 200 41 15 15 67 3 A 10 1.5 0.75 900 69 2500 −4 220 42 15 15 67 3 A 101.5 0.6 875 70 2600 −6 220

When the particle diameter of mixed powder was made as fine as 0.6 μm,sintering temperature further lowered by 25 to 50° C., and deflectivestrength also increased by about 10%. There was no change in electricalcharacteristics. Accordingly, by making particle diameter of mixedpowder 0.6 μm or below, a multi-layer resonance device having internalconductor made of silver, which has high electric conductivity and amelting point of 961° C., can be made.

Inorganic compounds other than those in the above exemplary embodimentcan be used as long as their contents are within the scope of thepresent invention and there is no detrimental effect on characteristics.

Ninth Exemplary Embodiment

Next, a range of compositions of glasses employed for the low-dielectriclayer of the diplexer of the present invention are explained. Thebonding strength between the low-dielectric layer and high-dielectriclayer, and sintering state such as delamination and waviness of asubstrate are evaluated from the appearance of a substrate made bysintering of such glasses and materials for the high-dielectric layer.Interfacial bonding strength was evaluated using a tensile test.Cracking of cut section when the substrate was cut using a dicer with0.2 mm thick blade at 1.0 mm/sec was also observed. The thermalexpansion coefficient of the glasses was measured using the TMA method,and the softening point was measured by DTA (Differential ThermalAnalysis) method.

Specimen Nos. 1 to 6 are low-dielectric materials with fixed amounts ofSiO₂—Al₂O₃—BaO—CaO—B₂O₃ amorphous glass mixed with a variable amount ofceramic powder of forsterite, zirconia, and alumina, and eachhigh-dielectric material of BCN, BCZCN, and BNTG sintered in accordancewith the first exemplary embodiment. Their evaluation results are shownin Table 7. Weight mixing ratio of amorphous glass and ceramic powder oflow-dielectric layer and ceramic powder is 50:50.

Low-dielectric material of specimen Nos. 1 to 5 showed slightly weakerbonding strength at an interface with BCN and BNTG but sintering waspossible. Integral sintering was not applicable to BCZCN, and thesintered body was damaged. The thermal expansion coefficient of BCN is93×10⁻⁷/° C., BNTG is 95×10⁻⁷/° C., but BCZN was a low 76×10⁻⁷/° C.Accordingly, the low-dielectric material of specimen Nos. 1 to 5 whichhave thermal expansion coefficients of 88 to 93×10³¹ ⁷/° C., relativelyclose to BCN and BNTG, were possible to sinter with BCN and BNTG, butthe sintered substance was damaged in the case of BCZN because a largecompression stress was assumed to have been applied to thehigh-dielectric layer.

TABLE 7 Specimen No. 1 2 3 4 5 6 7 8 Ceramic Forsterite 100 75 75 50 5050 50 25 powder (Mg₂SiO₄) Zirconia (ZrO₂) 0 25 0 50 20 5 0 0 Alumina(Al₂O₃) 0 0 25 0 30 45 50 75 Amorphous SiO₂ 50 50 50 50 50 50 50 50glass B₂O₃ 5 5 5 5 5 5 5 5 Al₂O₃ 5 5 5 5 5 5 5 5 BaO 20 20 20 20 20 2020 20 CaO 20 20 20 20 20 20 20 20 SrO 0 0 0 0 0 0 0 0 La₂O₃ 0 0 0 0 0 00 0 Softening point (_C) Weight ratio of ceramic powder: 50:50 50:5050:50 50:50 50:50 50:50 50:50 50:50 amorphous glass Characteristics α(/_C) 89 93 89 93 88 86 82 79 of low-dielectric d (μm) 3.0 3.1 2.9 3.02.9 2.8 3.1 3.2 material ε: (at 1 MHz) 6.8 8.2 6.9 8.8 8.1 7.6 7.5 7.8ρ: (logρ Ωcm) 13.2 12.8 12.9 12.9 13.3 13.3 13.2 13.1 Ts: (_C) 920 910910 900 900 910 910 890 BCN 1) Appearance ∘ ∘ ∘ ∘ ∘ ∘ ∘ del 2) Cracking∘ ⊚ ∘ ⊚ ∘ ∘ x — 3) Evaluation ∘ ∘ ∘ ∘ ∘ ∘ x x BCZCN 1) Appearance damdam dam dam dam ∘ ∘ ∘ 2) Cracking — — — — — x ∘ ⊚ 3) Evaluation x x x xx x ∘ ∘ BNTG 1) Appearance ∘ ∘ ∘ ∘ ∘ ∘ ∘ del 2) Cracking ∘ ⊚ ∘ ⊚ ∘ ∘ x —3) Evaluation ∘ ∘ ∘ ∘ ∘ ∘ x x Specimen No. 9 10 11 12 13 14 15 16Ceramic Forsterite 25 25 25 0 0 0 0 0 powder (Mg₂SiO₄) Zirconia (ZrO₂)75 25 50 100 75 50 25 0 Alumina (Al₂O₃) 0 50 25 0 25 50 75 100 AmorphousSiO₂ 50 50 50 50 50 50 50 50 glass B₂O₃ 5 5 5 5 5 5 5 5 Al₂O₃ 5 5 5 5 55 5 5 BaO 20 20 20 20 20 20 20 20 CaO 20 20 20 20 20 20 20 20 SrO 0 0 00 0 0 0 0 La₂O₃ 0 0 0 0 0 0 0 0 Softening point (_C) Weight ratio ofceramic powder: 50:50 50:50 50:50 50:50 50:50 50:50 50:50 50:50amorphous glass Characteristics α (/_C) 96 82 89 93 86 82 78 74 oflow-dielectric d (μm) 2.8 2.8 3.0 2.8 2.9 2.8 2.7 2.9 material ε: (at 1MHz) 9.2 8.2 9.1 10.2 9.5 9.3 8.6 8.1 ρ: (logρ Ωcm) 13.1 12.8 13.1 12.812.8 12.9 13.3 13.3 Ts: (_C) 890 890 890 890 890 900 890 890 BCN 1)Appearance ∘ del ∘ ∘ ∘ ∘ del del 2) Cracking ∘ — ∘ ⊚ ∘ x — — 3)Evaluation ∘ x ∘ ∘ ∘ x x x BCZCN 1) Appearance dam ∘ ∘ dam ∘ ∘ ∘ ∘ 2)Cracking — ∘ x — x ∘ ⊚ ⊚ 3) Evaluation x ∘ x x x ∘ ∘ ∘ BNTG 1)Appearance ∘ ∘ ∘ ∘ ∘ ∘ del del 2) Cracking ⊚ x ∘ ⊚ Δ x — — 3) Evaluation∘ x ∘ ∘ ∘ x x x α: Thermal expansion coefficient (/_C), d: Averageparticle diameter (μm), ε: Dielectric constant (at 1 MHz), ρ:Resistivity (logρ Ωcm), Ts: Sintering temperature (_C) del: Delaminated,dam: Damaged, wav: Waviness, wrp: Warpage, nst: Not sintered, 1)Appearance of sintered substance: x: Delaminated or damaged aftersintering, ∘: Can be sintered but low interfacial bonding strength, ⊚:Large bonding strength 2) Cracking of substrate: x: Damaged or manycracks after cutting, ∘: Some cracks, ⊚: No occurrence of cracks 3)Overall evaluation: x: Not acceptable, ∘: Good, ⊚: Excellent Thermalexpansion coefficient of high-dielectric material: BCN: 93 × 10⁻⁷/_C,BCZCN: 76 × 10⁻⁷/_C, BNTG: 93 × 10⁻⁷/_C, Specimen Nos. marked with *show that they fall outside the scope of Claims of the presentinvention.

Since the alumina content in the low-dielectric material of Specimen No.6 is higher, causing a reduced thermal expansion coefficient, sinteringwas also possible with BCZCN but large internal stresses built up,causing damage when released on cutting with the dicer.

Specimen No. 7 has increased alumina content, further reducing thethermal expansion coefficient. No cracks occurred in the cut sectionwhen cutting with the dicer after sintering with BCZCN. However, manycracks occurred in the high-dielectric layer when cutting the sinteredsubstance of BCN and BNTG with the dicer. This allows the assumption tobe made that cracks caused by large tensile stresses in thehigh-dielectric layer due to smaller thermal expansion coefficient inthe low-dielectric layer than the high-dielectric layer.

When the amount of alumina is farther increased and thermal expansioncoefficient falls to 79×10⁻⁷/° C., such as in Specimen No. 8, it cannotbe sintered with BCN and BNTG, and complete delamination occurred at theinterface (phase boundary). On the other hand, a good sintered substancewas achieved with BNTG although it showed somewhat weak bondingstrength.

The same tendency as in Specimen Nos. 1 to 8 was seen for Specimen Nos.9 to 16. When the amount of alumina exceeded 50% and thermal expansioncoefficient fell to a low level, sintering with BCZCN became possible,and when the amount of alumina is kept below 50% and thermal expansioncoefficient increased to a high level, sintering with BCN and BNTGbecame possible.

The above results indicate that the amount of alumina contained inceramic powder mixture containing forsterite, alumina, and zirconiashould ideally remain below 50 weight % when the high-dielectric layeris made of BCN or BNTG. If the high-dielectric layer is made of BCZCN,the amount of alumina contained should ideally exceed 50 weight %.

Tenth Exemplary Embodiment

Next, optimum components for the amorphous glass composition of thelow-dielectric layer were examined.

Here, BCN was used for the high-dielectric layer. Evaluation method isthe same as the second exemplary embodiment. Also, same as specimen No.1 in Table 7, 100 weight % of forsterite was used as ceramic powder forthe low-dielectric layer. Mixing weight ratio of amorphous glass andceramic powder was 50:50.

Specimen Nos. 1 and 17 to 20 in Table 8A were examined with regard tothe ratio of SiO₂ and MO (M is Ba and Ca) in amorphous glass. SiO₂ is anoxide for forming glass, and, at the same time, it functions as to lowerthe thermal expansion coefficient of glass. Therefore, if the amount ofSiO₂ is excessive (Specimen No. 20), the thermal expansion coefficientof the low-dielectric layer decreases and many cracks occur in thehigh-dielectric layer due to the same reason as described above. If theamount of SiO₂ is too little (Specimen No. 17), the thermal expansioncoefficient becomes too large and damages the sintered body.Accordingly, the amount of SiO₂ should ideally be kept between 40 and 50weight %.

Specimen Nos. 21 to 24 in Table 8A were examined with regard to theMO/La₂O₃ ratio. Amorphous glass of Specimen No. 19 was used as a base,and a part of MO (M is Ba and Ca) was replaced with La₂O₃. When theamount of La₂O₃ was increased, reactivity of BCN and the low-dielectricmaterial is improved, and bonding strength at the boundary is enhanced,but there was no change in thermal expansion coefficient. If the amountof La₂O₃ was excessive, however, reactivity of the low-dielectric layerand BCN became too strong, and waviness occurred in the entire sinteredbody. According to the results of specimen Nos. 17 to 24, the amount of(MO+La₂O₃) should ideally be kept between 40 and 50 weight % and theamount of La₂O₃ should ideally be 15 weight % or below.

In Specimen Nos. 25 to 39 in Table 8A and Table 8B, the optimum ratio ofBaO/CaO/SrO was examined, in Specimen Nos. 40 to 42, the optimum ratioof SiO₂/B₂O₃ was examined, and in Specimen Nos. 43 to 46, the optimumratio of Al₂O₃/SiO₂ was examined.

TABLE 8 Specimen No. 1 17* 18 19 20* 21 22 23 Ceramic Forsterite 100 100100 100 100 100 100 100 powder (Mg₂SiO₄) Zirconia (ZrO₂) 0 0 0 0 0 0 0 0Alumina (Al₂O₃) 0 0 0 0 0 0 0 0 Amorphous SiO₂ 50 35 40 45 55 45 45 45glass B₂O₃ 5 5 5 5 5 5 5 5 Al₂O₃ 5 5 5 5 5 5 5 5 BaO 20 30 30 25 20 2525 25 CaO 20 25 20 20 15 15 10 5 SrO 0 0 0 0 0 0 0 0 La₂O₃ 0 0 0 0 0 510 15 Softening point (_C) Weight ratio of ceramic powder: 50:50 50:5050:50 50:50 50:50 50:50 50:50 50:50 amorphous glass Characteristics α(/_C) 89 102 96 93 83 93 93 92 of low-dielectric d (μm) 3.0 2.8 2.9 3.13.1 3.0 3.1 2.9 material ε: (at 1 MHz) 6.8 7.3 7.2 7.0 6.5 7.0 7.0 6.9ρ: (logρ Ωcm) 13.2 12.5 12.8 13.0 13.5 13.2 13.1 13.1 Ts: (_C) 920 860890 900 930 890 890 890 BCN 1) Appearance ∘ dam ∘ ∘ ∘ ⊚ ⊚ ⊚ 2) Cracking∘ — ∘ ⊚ x ⊚ ⊚ ⊚ 3) Evaluation ∘ x ∘ ∘ x ⊚ ⊚ ⊚ Specimen No. 24* 25 26 2728 29 30 31 Ceramic Forsterite 100 100 100 100 100 100 100 100 powder(Mg₂SiO₄) Zirconia (ZrO₂) 0 0 0 0 0 0 0 0 Alumina (Al₂O₃) 0 0 0 0 0 0 00 Amorphous SiO₂ 45 45 45 45 45 45 45 45 glass B₂O₃ 5 5 5 5 5 5 5 5Al₂O₃ 5 5 5 5 5 5 5 5 BaO 25 40 35 30 20 10 5 0 CaO 0 0 5 10 20 30 35 40SrO 0 0 0 0 0 0 0 0 La₂O₃ 20 5 5 5 5 5 5 5 Softening point (_C) Weightratio of ceramic powder: 50:50 50:50 50:50 50:50 50:50 50:50 50:50 50:50amorphous glass Characteristics α (/_C) 92 87 89 91 94 96 100 102 oflow-dielectric d (μm) 2.8 2.8 2.9 3.2 3.1 2.8 3.2 3.1 material ε: (at 1MHz) 7.1 7.1 7.2 7.1 7.0 6.9 6.9 6.9 ρ: (logρ Ωcm) 13.2 13.2 13.5 12.812.8 13.2 13.3 13.4 Ts: (_C) 880 900 900 890 890 890 880 880 BCN 1)Appearance wav ∘ ⊚ ⊚ ⊚ ∘ ∘ ∘ 2) Cracking — ∘ ⊚ ⊚ ∘ ∘ x x 3) Evaluation x∘ ⊚ ⊚ ∘ ∘ x x Specimen No. 32 33 34 35 36 37 38 39 Ceramic Forsterite100 100 100 100 100 100 100 100 powder (Mg₂SiO₄) Zirconia (ZrO₂) 0 0 0 00 0 0 0 Alumina (Al₂O₃) 0 0 0 0 0 0 0 0 Amorphous SiO₂ 45 45 45 45 45 4545 45 glass B₂O₃ 5 5 5 5 5 5 5 5 Al₂O₃ 5 5 5 5 5 5 5 5 BaO 0 10 20 30 350 0 0 CaO 0 0 0 0 0 10 20 30 SrO 40 30 20 10 5 30 20 10 La₂O₃ 5 5 5 5 55 5 5 Softening point (_C) Weight ratio of ceramic powder: 50:50 50:5050:50 50:50 50:50 50:50 50:50 50:50 amorphous glass Characteristics α(/_C) 80 82 83 87 89 83 85 91 of low-dielectric d (μm) 2.9 3.2 2.9 2.92.8 2.8 2.9 2.9 material ε: (at 1 MHz) 7.2 7.1 7.1 7.2 7.1 7.2 7.2 7.1ρ: (logρ Ωcm) 13.2 12.5 12.7 12.2 12.8 12.7 12.9 12.9 Ts: (_C) 860 880880 890 890 880 880 880 BCN 1) Appearance del del del ∘ ⊚ del del ⊚ 2)Cracking — — — ∘ ∘ — — ⊚ 3) Evaluation x x x ∘ ∘ x x ⊚ Specimen No. 4041* 42 43 44 45* 46 Ceramic Forsterite 100 100 100 100 100 100 100powder (Mg₂SiO₄) Zirconia (ZrO₂) 0 0 0 0 0 0 0 Alumina (Al₂O₃) 0 0 0 0 00 0 Amorphous SiO₂ 40 35 50 40 35 30 50 glass B₂O₃ 10 15 0 5 5 5 5 Al₂O₃5 5 5 10 15 20 0 BaO 25 25 25 25 25 25 25 CaO 10 10 10 10 10 10 10 SrO 00 0 0 0 0 0 La₂O₃ 0 0 0 0 0 0 0 Softening point (_C) Weight ratio ofceramic powder: 50:50 50:50 50:50 50:50 50:50 50:50 50:50 amorphousglass Characteristics α (/_C) 93 92 95 94 95 98 90 of low-dielectric d(μm) 2.9 2.9 2.8 2.9 2.9 2.9 3.1 material ε: (at 1 MHz) 6.9 7.2 6.8 7.37.3 7.4 6.9 ρ: (logρ Ωcm) 12.8 12.8 12.9 12.9 12.8 12.8 13.2 Ts: (_C)890 850 910 890 890 890 900 BCN 1) Appearance ∘ wav ∘ ∘ ∘ ∘ ∘ 2)Cracking ⊚ — ⊚ ⊚ ∘ x ⊚ 3) Evaluation ∘ x ∘ ∘ ∘ x ∘ α: Thermal expansioncoefficient (/_C), d: Average particle diameter (μm), ε: Dielectricconstant (at 1 MHz), ρ: Resistivity (logρ Ωcm), Ts: Sinteringtemperature (_C) del: Delaminated, dam: Damaged, wav: Waviness, wrp:Warpage, nst: Not sintered, 1) Appearance of sintered substance: x:Delaminated or damaged after sintering, ∘: Can be sintered but lowinterfacial bonding strength, ⊚: Large bonding strength 2) Cracking ofsubstrate: x: Damaged or many cracks after cutting, ∘: Some cracks, ⊚:No occurrence of cracks 3) Overall evaluation: x: Not acceptable, ∘:Good, ⊚: Excellent Thermal expansion coefficient of high-dielectricmaterial: BCN: 93 × 10⁻⁷/_C, BCZCN: 76 × 10⁻⁷/_C, BNTG: 93 × 10⁻⁷/_C,Specimen Nos. marked with * show that they fall outside the scope ofClaims of the present invention.

According to the results of Specimen Nos. 25 to 39, BaO should ideallybe 10 to 40 weight %, CaO is 0 to 30 weight %, and SrO is 0 to 10 weight%. When the amount of BaO and SrO is increased, the material will havelower thermal expansion, and when the content of CaO is increased, thematerial will have higher thermal expansion.

According to the results of Specimen Nos. 40 to 42, the amount of B₂O₃should ideally be 0 to 10 weight %. When B₂O₃ exceeds 10 weight %, glasssoftening point decreases too much, and causes strong reactivity withthe high-dielectric layer, resulting in waviness of the sintered body.

According to the results of Specimen Nos. 43 to 46, the amount of Al₂O₃should ideally be 0 to 15 weight % because when it exceeds 15 weight %,the thermal expansion becomes too large and causes cracks in thehigh-dielectric layer.

The present invention is not limited to the third exemplary embodiment.Other components such as SnO₂, P₂O₅, and K₂O can be added to amorphousglass of the low-dielectric layer.

Eleventh Exemplary Embodiment

Next, the mixing weight ratio of amorphous glass and ceramic powder wasexamined. The composition of Specimen No. 21 was employed as thecomposition of amorphous glass according to the results of the tenthexemplary embodiment.

Specimen Nos. 21 and 47 to 52 in Table 9 uses forsterite as ceramicpowder, and the mixing weight ratio of forsterite and amorphous glasswas changed for examination. Specimen Nos. 53 to 59 use alumina asceramic powder and specimen Nos. 60 and 61 show results when zirconia isused.

In any ceramic powder, sintering performance of the low-dielectric layermaterial drops when the mixing weight ratio of ceramic powder becomeslarge. When the mixing weight ratio of ceramic powder and amorphousglass reaches 75:25, the low-dielectric layer material cannot besintered even at 950° C., causing degradation in insulation resistance.If the material is sintered at higher temperature, it became impossibleto sinter with silver.

On the other hand, if the mixing ratio of amorphous glass increases,sintering performance improved but reactivity with the high-dielectriclayer became too strong when the mixing ratio reaches 25:75, causingwarpage or waviness of the sintered body.

Based on the above results, the mixing weight ratio of ceramic powderand amorphous glass should ideally be between 30:70 and 70:30.

TABLE 9 Specimen No. 21 47 48 49* 50 51 52* 53* Ceramic Forsterite 100100 100 100 100 100 100 0 powder (Mg₂SiO₄) Zirconia (ZrO₂) 0 0 0 0 0 0 00 Alumina (Al₂O₃) 0 0 0 0 0 0 0 100 Amorphous SiO₂ 45 45 45 45 45 45 4545 glass B₂O₃ 5 5 5 5 5 5 5 5 Al₂O₃ 5 5 5 5 5 5 5 5 BaO 25 25 25 25 2525 25 25 CaO 15 15 15 15 15 15 15 15 SrO 0 0 0 0 0 0 0 0 La₂O₃ 5 5 5 5 55 5 5 Softening point (_C) Weight ratio of ceramic powder: 50:50 40:6030:70 25:75 60:40 70:30 75:25 75:25 amorphous glass Characteristics α(/_C) 93 92 93 92 92 93 93 76 of low-dielectric d (μm) 3.0 2.9 2.9 3.12.9 2.9 2.8 3.2 material ε: (at 1 MHz) 7.0 7.2 7.4 7.5 6.9 6.4 5.9 6.8ρ: (logρ Ωcm) 13.2 13.1 13.3 13.3 12.5 11.6 10.5 9.8 Ts: (_C) 890 870860 850 910 950 950 950 BCN 1) Appearance ⊚ ⊚ ∘ wrp ⊚ ∘ nst del 2)Cracking ⊚ ⊚ ⊚ — ⊚ ⊚ ⊚ — 3) Evaluation ⊚ ⊚ ⊚ x ⊚ ∘ x x BCZCN 1)Appearance dam dam dam dam dam dam dam nst 2) Cracking — — — — — — — ⊚3) Evaluation x x x x x x x x BNTG 1) Appearance ⊚ ⊚ ∘ wrp ∘ ∘ nst del2) Cracking ⊚ ⊚ ⊚ — ⊚ ⊚ ⊚ — 3) Evaluation ⊚ ⊚ ⊚ x ∘ ∘ x x Specimen No.54 55 56 57 58 59 60 61 Ceramic Forsterite 0 0 0 0 0 0 0 0 powder(Mg₂SiO₄) Zirconia (ZrO₂) 0 0 0 0 0 0 100 100 Alumina (Al₂O₃) 100 100100 100 100 100 0 0 Amorphous SiO₂ 45 45 45 45 45 45 45 45 glass B₂O₃ 55 5 5 5 5 5 5 Al₂O₃ 5 5 5 5 5 5 5 5 BaO 25 25 25 25 25 25 25 25 CaO 1515 15 15 15 15 15 15 SrO 0 0 0 0 0 0 0 0 La₂O₃ 5 5 5 5 5 5 5 5 Softeningpoint (_C) Weight ratio of ceramic powder: 70:30 60:40 50:50 40:60 30:7025:75 70:30 30:70 amorphous glass Characteristics α (/_C) 76 76 77 77 7777 94 95 of low-dielectric d (μm) 3.3 3.2 3.3 3.1 3.2 3.2 2.7 2.9material ε: (at 1 MHz) 7.6 8.1 8.0 7.9 7.9 7.9 8.2 8.4 ρ: (logρ Ωcm)11.1 12.1 12.8 13.1 13.1 13.3 13.3 13.3 Ts: (_C) 950 920 900 880 870 850950 860 BCN 1) Appearance del del del del del del ∘ ⊚ 2) Cracking — — —— — — ⊚ ⊚ 3) Evaluation x x x x x x ∘ ⊚ BCZCN 1) Appearance ∘ ∘ ⊚ ⊚ ⊚wav dam dam 2) Cracking ⊚ ⊚ ⊚ ⊚ ⊚ — — — 3) Evaluation ∘ ∘ ⊚ ⊚ ⊚ x x xBNTG 1) Appearance del del del del del del ∘ ⊚ 2) Cracking — — — — — — ⊚⊚ 3) Evaluation x x x x x x ∘ ⊚ α: Thermal expansion coefficient (/_C),d: Average particle diameter (μm), ε: Dielectric constant (at 1 MHz), ρ:Resistivity (logρ Ωcm), Ts: Sintering temperature (_C) del: Delaminated,dam: Damaged, wav: Waviness, wrp: Warpage, nst: Not sintered, 1)Appearance of sintered substance: x: Delaminated or damaged aftersintering, ∘: Can be sintered but low interfacial bonding strength, ⊚:Large bonding strength 2) Cracking of substrate: x: Damaged or manycracks after cutting, ∘: Some cracks, ⊚: No occurrence of cracks 3)Overall evaluation: x: Not acceptable, ∘: Good, ⊚: Excellent Thermalexpansion coefficient of high-dielectric material: BCN: 93 × 10⁻⁷/_C,BCZCN: 76 × 10⁻⁷/_C, BNTG: 93 × 10⁻⁷/_C, Specimen Nos. marked with *show that they fall outside the scope of Claims of the presentinvention.

Twelfth Exemplary Embodiment

Next, the effect of average ground particle diameter of thelow-dielectric material to low temperature sintering of thelow-dielectric material was examined.

Specimen No. 51 in Table 9 can finally be sintered at 950° C., the limittemperature for sintering with silver, when the mixing weight ratio ofceramic powder (forsterite) and amorphous glass is 70:30. Specimen Nos.63 and 64 in Table 10 show results of grinding this low-dielectricmaterial longer for reducing the average particle diameter to achievesintering at lower temperature. When the average ground particlediameter of the low-dielectric material is 2.0 μm or below, sinteringtemperature fell more than 20° C. Those compositions, such as SpecimenNo. 51, with somewhat lower sintering performance can also secure morethan 30° C. difference with melting temperature (about 960° C.) ofsilver. Accordingly, partial melting of silver electrode or degradationin conductivity can be prevented.

Thus, the average particle diameter of the low-dielectric materialshould ideally be 2.0 μm or below.

TABLE 10 Specimen No. 51 63 64 65 66 67* 68 69 70* 71 72 73* CeramicForsterite 100 100 100 100 100 100 100 100 100 100 100 100 powder(Mg₂SiO₄) Zirconia (ZrO₂) 0 0 0 0 0 0 0 0 0 0 0 0 Alumina (Al₂O₃) 0 0 00 0 0 0 0 0 0 0 0 Amorphous SiO₂ 45 45 45 45 45 45 45 45 45 45 45 45glass B₂O₃ 5 5 5 5 5 5 5 5 5 5 5 5 Al₂O₃ 5 5 5 5 5 5 5 5 5 5 5 5 BaO 2525 25 25 25 25 25 25 25 25 25 25 CaO 15 15 15 15 15 15 15 15 15 15 15 15SrO 0 0 0 0 0 0 0 0 0 0 0 0 La₂O₃ 5 5 5 5 5 5 5 5 5 5 5 5 Softeningpoint (_C) Weight ratio of ceramic powder: 70:30 70:30 70:30 70:30 70:3070:30 70:30 70:30 70:30 70:30 70:30 70:30 amorphous glass SiO₂ — — —0.05 2.0 3.0 — — — — — — CuO — — — — — — 0.05 2.0 3.0 — — — MnO₂ — — — —— — — — — 0.05 2.0 3.0 Characteristics α (/_C) 93 93 93 93 91 91 93 9393 93 93 93 of low- d (μm) 2.9 2.0 1.5 3.0 3.1 2.9 2.9 2.8 2.9 3.1 2.83.1 dielectric ε: (at 1 MHz) 6.4 7.1 7.1 6.9 6.9 6.8 7.0 7.0 7.1 7.1 7.37.3 material ρ: (logρ Ωcm) 11.6 13.2 13.2 12.8 12.8 12.4 12.8 12.1 10.812.7 12.5 11.2 Ts: (_C) 950 930 920 940 930 920 920 920 910 930 930 930BCN 1) Appearance ∘ ⊚ ⊚ ⊚ ⊚ wav ⊚ ⊚ ⊚ ∘ ⊚ ⊚ 2) Cracking ⊚ ⊚ ⊚ ⊚ ⊚ — ⊚ ⊚⊚ ⊚ ⊚ ⊚ 3) Evaluation ∘ ⊚ ⊚ ⊚ ⊚ x ⊚ ⊚ ⊚ ∘ ⊚ ⊚ BNTG 1) Appearance ∘ ⊚ ⊚ ⊚⊚ wav ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 2) Cracking ⊚ ⊚ ⊚ ⊚ ⊚ — ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ 3) Evaluation ∘ ⊚⊚ ⊚ ⊚ x ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ α: Thermal expansion coefficient (/_C), d: Averageparticle diameter (μm), ε: Dielectric constant (at 1 MHz), ρ:Resistivity (logρ Ωcm), Ts: Sintering temperature (_C) del: Delaminated,dam: Damaged, wav: Waviness, wrp: Warpage, nst: Not sintered, 1)Appearance of sintered substance: x: Delaminated or damaged aftersintering, ∘: Can be sintered but low interfacial bonding strength, ⊚:Large bonding strength 2) Cracking of substrate: x: Damaged or manycracks after cutting, ∘: Some cracks, ⊚: No occurrence of cracks 3)Overall evaluation: x: Not acceptable, ∘: Good, ⊚: Excellent Thermalexpansion coefficient of high-dielectric material: BCN: 93 × 10⁻⁷/_C,BCZCN: 76 × 10⁻⁷/_C, BNTG: 93 × 10⁻⁷/_C, Specimen Nos. marked with *show that they fall outside the scope of Claims of the presentinvention.

Thirteenth Exemplary Embodiment

Next, the effect of subcomponent added to the low-dielectric material tolower sintering temperature of the low-dielectric material was examined.

Specimen Nos. 65 to 67 in Table 10 show results of evaluation whensilicon dioxide (SiO₂) is added as subcomponent, and Specimen Nos. 68 to70 are when copper oxide (CuO) is added, and Specimen Nos. 71 to 73 arewhen manganese dioxide (MnO₂) is added.

In any subcomponent, sintering temperature dropped more than 20° C., andshowed good effect on low-temperature sintering. However, when silicondioxide is used as subcomponent, waviness occurred in the sintered bodywhen it was added for 3.0 weight %. When copper oxide or manganesedioxide was added for 3.0 weight %, insulation resistance of thelow-dielectric material degraded, and became 1×10¹² (Ωcm) or below.

According to the above results, silicon dioxide, copper oxide, ormanganese dioxide should ideally be added for 0.05 to 2.0 weight % assubcomponent.

Accordingly, the low-dielectric material of the diplexer of the presentinvention can be sintered with the dielectric ceramic material of BCN,BCZCN, or BNTG for high-dielectric micro wave by mixing amorphous glassand ceramic powder. This prevents delamination at bonding interface ofdifferent materials of the sintered body and cracking in each layer,offering the diplexer with higher reliability and stability.

INDUSTRIAL APPLICABILITY

The present invention offers a simple circuit configuration of adiplexer comprising a low-pass filter, band-pass filter, and matchingcircuit; and facilitates the setting of the low-pass filter withoutaffecting the passband of the band-pass filter.

Moreover, the present invention enables the reduction of the size of thediplexer by forming the low-dielectric layer and high-dielectric layer.The low-pass filter and the matching circuit of the low-pass filter areformed in the low-dielectric layer, and the band-pass filter andmatching circuit of the band-pass filter are formed in thehigh-dielectric layer.

Furthermore, the present invention offers a diplexer with highreliability and stability which prevents delamination or cracking byoptimizing the material composition of the high-dielectric layer and thelow-dielectric layer.

Reference Numerals

101 first capacitor

102 first inductor

103 second capacitor

104 third capacitor

105 second inductor

106 fourth capacitor

107 first quarter wavelength resonator

108 fifth capacitor

109 third inductor

110 second quarter wavelength resonator

111 sixth capacitor

112 first terminal

113 common terminal

114 second terminal

115 low-pass filter

116 band-pass filter

What is claimed is:
 1. A diplexer separating a signal into two frequencybands, comprising: a first terminal, a second terminal, and a commonterminal; a low-pass filter, coupled between said first terminal andsaid common terminal, whose passband is a first band, a band-passfilter, coupled between said common terminal and said second terminal,whose passband is a second band which is higher in frequency than saidfirst band; a first matching circuit, coupled between said low-passfilter and said common terminal, for raising impedance of said firstmatching circuit in said second band; and a second matching circuit,coupled between said common terminal and said band-pass filter, forraising impedance of said second matching circuit in said first band,wherein at least two layers of a high-dielectric layer andlow-dielectric layer are laminated, said band-pass filter and saidsecond matching circuit are formed in said high-dielectric layer, andsaid low-pass filter and said first matching circuit are formed in saidlow-dielectric layer.
 2. A diplexer as defined in claim 1, wherein aresonator electrode and capacitor electrode form said band-pass filter,a capacitor electrode for forming said second matching circuit isdisposed in a high-dielectric layer; an inductor electrode and capacitorelectrode forms said low-pass filter, an inductor electrode for formingsaid first matching circuit is disposed in said low-pass filter; and acommon shield electrode for said band-pass filter and said low-passfilter is disposed on an interface between said high-dielectric layerand said low-dielectric layer.
 3. A diplexer as defined in claim 1,wherein a resonator electrode, capacitor electrode, and shield electrodeform said band-pass filter, a capacitor electrode for forming saidsecond matching circuit is disposed in a high-dielectric layer; and aninductor electrode, capacitor electrode, and shield electrode form saidlow-pass filter, and an inductor electrode for forming said firstmatching circuit is disposed in a low-dielectric layer.
 4. A diplexer asdefined in claim 1, wherein said low-dielectric layer is composed ofceramic powder of at least one of forsterite (Mg₂SiO₄), zirconia (ZrO₂),and alumina (Al₂O₃), and amorphous glass.
 5. A diplexer as defined inclaim 4, wherein a mixing weight ratio of said ceramic powder and saidamorphous glass is between 30:70 and 70:30.
 6. A diplexer as defined inclaim 4, wherein said amorphous glass of said low-dielectric layerincludes SiO₂—Al₂O₃—MO(M is at least one of Ba, Ca, and Sr)—La₂O₃—B₂O₃.7. A diplexer as defined in claim 6, wherein major components of saidamorphous glass includes 40 to 50 weight % of SiO₂, 0 to 15 weight % ofAl₂O₃, 0 to 10 weight % of B₂O₃, and 40 to 50 weight % of MO (M is atleast one of Ba, Ca, and Sr)+La₂O₃, and 0 to 15 weight % of La₂O₃.
 8. Adiplexer as defined in claim 6, wherein 0.05 to 2.0 weight % convertinginto SiO₂, CuO and MnO₂ of at least one of silicone oxide, copper oxide,or manganese oxide is added as a sub-component of said low-dielectriclayer when the total amount of said ceramic powder and amorphous glassis 100 weight %.
 9. A diplexer as defined in claim 1, wherein saidhigh-dielectric layer is a dielectric ceramic material which includesBi₂O₃, CaO, and Nb₂O₅.
 10. A diplexer as defined in claim 1, whereinsaid high-dielectric layer is a dielectric ceramic material whichincludes Bi₂O₃, CaO, ZnO, CuO, and Nb₂O₅.
 11. A diplexer as defined inclaim 1, wherein said high-dielectric layer is a dielectric ceramicmaterial which includes BaO, Nd₂O₅, TiO₂, and glass.
 12. A diplexer asdefined in claim 11, wherein said dielectric ceramic material comprisinga first component which can be defined by a general formula asxBaO—yNd₂O₅—zTiO₂—wBi₂O₃ (x+y+z+w=1), said x, y, z, and w arerespectively within 0.1≦x≦0.2, 0.1≦y≦0.2, 0.55≦z≦0.8, and 0.005≦w≦0.05;and a second component which is a glass at least containing SiO₂, Al₂O₃,MO (M is at least one of Ba, Ca, and Sr), La₂O₃, and B₂O₃; and saidsecond component accounting for between 3 weight % and 50 weight %against 100 weight % of said first component.
 13. A diplexer as definedin claim 12, wherein glass component of said second component comprising40 to 50 weight % of SiO₂, 0 to 15 weight % of Al₂O₃, 0 to 10 weight %of B₂O₃, and 40 to 50 weight % of MO (M is at least one of Ba, Ca, andSr)+La₂O₃, and 0 to 15 weight % of La₂O₃.
 14. A diplexer as defined inclaim 12, wherein copper oxide converting into CuO is added as asubcomponent accounting for less than 5 weight % against 100 weight % ofsaid first component.